I can't bear to part with any of my nappies, they all get used at one time or another, even if not very often, and I am DEFINATELY (fingers crossed) having another baby, so will get use out of them then.
So I voted keep them as that is exactly what I am doing.
Although having said that, I have recently sold all of my Huggles as I didn't like them anymore and knew I would never uee them again as I have replaced them with Stuffies and also I had 5 Fluffles so sold 3 - even though they are not my favourite, they come in handy for quick drying and being fleece lined. So maybe just sell a few of your least favourites.
All of my nappies are onesize or size 2 so I am going to have some fun buying some newborn nappies for the next one (I have some I use for demos already but will get a few more) and then will use all of these. So I can't see the point in selling them.